Hydraulic clearance compensating device

ABSTRACT

A hydraulic clearance compensating device for controlling the motor valves of an internal combustion engine. The device has a piston which is longitudinally displaceable within a cylinder, said piston having an antechamber therein which is connected to a supply of oil which serves as the working agent in the device. A one-way check valve allows oil to enter a pressure chamber adjacent one end of the piston from the antechamber. Recycle of oil leaking from the ring gap between the piston and cylinder back into the antechamber is accomplished by means of a recess formed on the exterior of the piston, said recess communicating with at least one transverse bore which is connected to the antechamber.

United States Patent 1191 Fleischer et a1. 1 1 Aug. 5, 1975 1 1 1 HYDRAULIC CLEARANCE 2,667.149 l/1954 Purchas 123/90155 COMPENSATING DEVICE 2,908,260 10/1959 Bergmann 1 1 1 w 123/9055 2.943.611 7/1960 Dadd 1 1 v 1. 123/9055 [75] Inventors: Volkmar Fleischer, Herrenkamp; 2 5 557 10 1960 Dadd 123 9055 Johannes Friedl, Wolfsburg, both of 3,048,156 8/1962 Van Slooten 1. 123/9055 Germany [73] Assignee: Volkswagenwerk Aktiengesellschal't, Emmi-n" Char1e5 Myhre WOKSburgy Germany Assistant [imminer-Daniel J1 O'Connor Attorney. Agent, or FirmBrumbaugh Graves, Flledl Sept. 11, Donohue & Raymond [21] Appl. N0.: 396,220

[57] ABSTRACT Forelgn Apphcmlo" Pnonty Data A hydraulic clearance compensating device for con- P 1972 Germany 2245666 trolling the motor valves of an internal combustion engine. The device has a piston which is longitudinally [52] US. Cl 1. 123/9055; 123/9036 displaceable within a fi d said piston having an [51] Int. Cl. F011 l/14 antechamber therein which is connected to a Supp|y f [58] Field of Search 123/9055, 90.57, 90.59, i which serves as the working agent in the device A 123/9058, -36 one-way check valve allows oil to enter a pressure chamber adjacent one end of the piston from the ante- 1 1 Referellcvi Cited chamber. Recycle of oil leaking from the ring gap be- UNITED STATES PATENTS tween the piston and cylinder back into the antecham- 1,346,116 7/1920 De Waters 123/9036 bet is accomplished y means of a remiss formed on 1,455,244 5 1923 F eu 123 903 the exterior of the piston, said recess communicating 1,624,497 4/1927 McAllister 1 1 1 123/9036 with at least one transverse bore which is connected to 1,930,368 10/1933 Nelson 1. 123/9036 the antechambep 2.322172 6/1943 Spencer.... 1. 123/9036 2,322,173 6/1943 Spencer 123/9036 5 Claims, 1 Drawing Figure HYDRAULIC CLEARANCE COMPENSATING DEVICE BACKGROUND OF THE INVENTION The present invention is a hydraulic clearance compensating device for controlling the valves of an internal combustion engine. In such a device a piston is longitudinally displaceable within a cylinder and encloses a pressure space adjacent one end of the piston. A nonreturn or one-way valve communicatively connected with an antechamber within the piston allows oil to enter the pressure space from the antechamber. The oil is supplied from the rocker lever, which actuates the engine valve.

DESCRIPTION OF THE PRIOR ART One example of a typical hydraulic clearance compensating device is described in British Pat. No. 998,350. In this device, oil is continuously leaking from the ring gap lying between the piston and the cylinder and must be replaced by the admission of new oil. In order to prevent any air which may be included in this new oil from being admitted into the pressure space, the antechamber, which is disposed in that device within the hollow valve push rod, is made ofa relatively large size, and if desired, can be provided with a special ventilating bore. Such a design for a hydraulic clearance compensating device is suitable, however, only for a vertical arrangement of the hydraulic element. If the arrangement were made horizontal the design would not exclude the danger that air would not also be admitted into the pressure space when fresh oil is added to compensate for the leakage of oil during operation of the device. The admission of such fresh oil is particularly needed when the motor is operated at high speed. The admittance of air, which is compressible rather than being incompressible as is oil, is naturally undesirable since it causes a substantial increase in the sink-in value of the hydraulic element, an alteration of the valve opening times, and an increase in the lifting and touch-down rates for the motor valve. Any increase in the touch-down rates of the valves causes a corresponding increase in the mechanical stresses to which the engine is subjected, and this frequently leads to mechanical deterioration of the clearance-compensating device and other parts of the motor valve control system.

Other hydraulic clearance compensating devices are known, e.g., in German Pat. No. l,984,827, wherein new oil is supplied through a plurality of oil flow pathways from a hollow push rod which is driven by the cam shaft. The oil which is supplied in that apparatus is the oil which is required not only for compensating for the oil losses leaking through the ring gap between the piston and cylinder but also the oil required for lubricating the bearing of the valve rocker. Despite considerable work expended in designing such devices, it has not been possible to insure the exclusive admittance of airfree oil into the pressure space of the hydraulic element. The danger of admitting air-containing oil is particularly high in these devices, unlike the first type referred to above, since the hydraulic elements are connected in the middle of the oil supply chain and considerable foaming therein occurs during extended periods at high rates of revolution. In the first type of device the hydraulic element is connected as the last member of the oil supply chain, and this avoids having the oil required for lubrication flow through the antechamber or having additional air accumulation occur within the antechamber.

Therefore, the present invention is based on the problem of providing, on the basis of the initially mentioned design, a hydraulic clearance compensating device which substantially excludes the danger of air admittance into the pressure chamber and, moreover, which is also suitable for horizontal installation positions.

SUMMARY OF THE INVENTION The present invention solves the aforesaid shortcomings of the apparatus known to the prior art by including means to recycle oil back into the antechamber when it leaks from the pressure chamber through the ring gap. By means of this construction a substantially closed oil circulation system is provided. Since no losses of oil occur to the outside of this system, there is no need for admittance of fresh oil which normally entails the danger of admittance of air as well.

BRIEF DESCRIPTION OF THE DRAWING The invention described and claimed herein is best understood by reference to the description of the invention in light of the drawing which also forms a portion of this specification wherein:

The FIGURE is a partial cross-sectional view, partially broken away showing the hydraulic clearance compensating device of the present invention.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The FIGURE shows a ram means 1 which transmits the oscillatory motion caused by rotation of the cam shaft (not shown in the FIGURE) to the motor valve (also not shown in the FIGURE) by way of a push rod 2 located adjacent the cam shaft, a hydraulic clearance compensating element 3, and a valve rocker 13. The hydraulic clearance compensating element 3, comprises a cylinder 10 which is connected to the push rod 2, and a piston 9 which is slidably disposed within the cylinder. A ring gap 8 (shown greatly enlarged in the FIGURE) is situated between the piston and the cylinder. The piston 9 is hollow and is provided with an internal antechamber 4 that connects by means of a boring 7 to the pressure chamber 5 which is enclosed between the piston 9 and the cylinder 10 and which lies adjacent one end of the piston 9. Access through the connection between the antechamber 4 and the pressure chamber 5 is controlled by a non-return or oneway valve which comprises a ball 6, a spring 19 and a valve cap 18 which holds the ball and spring. The valve cap 18 is pressed or urged against the piston 9 by means of a screw spring 20 which is disposed within the pressure chamber 5 and which allows for the return of the piston 9 to its rest position. Any oil exiting through the ring gap 8 from the pressure chamber 5 is collected in a recess or groove 12 in the outer surface of the piston 9, and is recycled into antechamber 4 through at least one traverse boring 21 which communicates at one of its ends with the recess 12 and at its other end with the antechamber 4. The ring gap 8 is sealed towards the outside, i.e., adjacent the side of the recess 12 which is remote from the non-return valve, by means of a seal 23 disposed within the cylinder 10 in the ring gap.

The extended portion of the piston 9, which is ball head ll, is connected with a rocker 13 which is rotably supported on a hollow rocker shaft 17. Oil required for the hydraulic clearance compensating element 3 is first sent by way of a hollow space 16 in the rocker shaft 17, into an oil ventilating space 14 disposed in the rocker 13. This ventilating space is sufficiently large to accomodate the entire oil volume required for the pressure chamber and is open at its top, or on its upwardly facing surface, so that any air contained in the oil collected within the space may readily be evacuated from that space. The oil ventilating space 14 is connected with antechamber 4 by way of a single oil flow path, i.e., connection borehole l5 and a borehole 22, which is provided within the ball head 11.

By sealing off the ring gap 8 residing between the piston 9 and the cylinder 10 from the outside and by recycling any leaking oil back into antechamber 4 by way of the ring gap, through the recess 12 and transverse bore 2l, a nearly closed circulation of oil is obtained for the hydraulic clearance compensating element 3. Since no oil losses occur to the outside, the hydraulic clearance compensating element 3 of the present invention does not require any admittance of fresh oil during operation. This excludes the possibility of admitting any air into the antechamber 4 and from there into pressure chamber 5 of the hydraulic clearancecompensating element 3.

Only when the engine is started up again after extended periods of non-use, does it become necessary to supply the hydraulic clearance compensating element 3 with oil, since during extended periods of inoperation the hydraulic clearance compensating element when connected with an open motor valve and when loaded by the motor valve spring will move to its fully con tracted position due to removal of oil from the pressure chamber during those periods of inoperation. When the engine is subsequently started up again, the hydraulic clearance compensating element 3 will immediately suck in the entire volume of oil needed for pressure chamber 5. In order to prevent inclusions of air with this admission of the fresh oil, the rocker I3 is provided with an oil ventilating space 14 which has a volume which is at least equal to the volume of oil capable of being held in the pressure chamber. The volume of oil kept in the ventilating space during prolonged periods of engine inactivity will then be air-free.

The hydraulic clearance compensating element of the present invention with its substantially closed oil circulation system may also be advantageously used in a horizontal operating position since such a type of position or arrangement excludes the danger of any accumulation of air inclusions within antechamber 4. The faultless functioning of the device according to the present invention requires a one-time filling with airfree oil and reliably ensures during subsequent periods of time faultless operation without the danger of mechanical damage or destruction of the motor valve control parts. Changes or alterations in the valve-lift periods is impossible by virtue of the present invention.

A person of skill in the art will become aware of modifications which can be made to the invention described herein without the exercise of inventive skill. Such modifications which do not depart from the spirit and scope of this invention are intended to be included since the foregoing is merely illustrative of certain preferred embodiments of the invention. The appended claims define the scope of protection sought.

We claim:

1. A hydraulic clearance compensating system for controlling the motor valves of an internal combustion engine, comprising:

a rocker arm having an oil flow channel and an oil ventilating space formed therein;

a hydraulic clearance compensating device including a cylinder and a piston which is longitudinally displaceable with said cylinder, said piston and cylinder having a ring gap therebetween;

an antechamber in said piston;

means, including a port in said antechamber, sealingly communicating with said rocker arm for establishing a fluid-tight oil flow path between said antechamber and said oil ventilating space;

a pressure chamber adjacent one end of the cylinder which is communicatively connected to said antechamber within the piston by means of a nonreturn valve, said antechamber having means to hold oil supplied by said rocker arm, said antechamber receiving oil solely by way of said oil flow path and a transverse bore means communicating between the ring gap and the antechamber by which oil leaking from the pressure chamber is recycled back to the antechamber, the antechamber being otherwise sealed and having means to exclude air from said antechamber and said pressure chamber.

2. A device as claimed in claim 1 wherein the ventilating space has a volume which is at least equal to the volume of oil capable of being held in the pressure chamber.

3. A hydraulic clearance compensating system for controlling motor valves of an internal combustion engine having a pressurized oil supply system, comprising:

a rocker arm including means therein defining an oil ventilating space, said ventilating space being fed with oil from the oil supply system and having means such that, when the oil supply system is depressurized, the oil in said ventilating space does not drain out through the oil supply system;

a hydraulic clearance compensating device including a cylinder and a piston longitudinally displaceable within said cylinder, said piston and cylinder having a ring gap therebetween; means in said piston defining an antechamber; a pressure chamber in said cylinder adjacent one end thereof; fluid passage means communicating between said antechamber and said pressure chamber; a non-return valve in said fluid passage for permitting oil flow through said passage only toward said pressure chamber; said antechamber communicating with said ventilating space and having means to receive and hold oil supplied through said ventilating space in said rocker arm; means to recycle oil leaking from said pressure chamber through said ring gap back into said antechamber; said recycling means including a recess formed on the exterior of said piston in said ring s p;

means defining at least one transverse bore communicating between said recess and said antechamber;

a seal disposed in said ring gap and located adjacent the side of the recess remote from the non-return valve.

4. A hydraulic clearance compensating system for controlling the motor valves of an internal combustion engine, comprising:

a rocker arm pivotally mounted on a shaft having a horizontal axis, said rocker arm having means formed therein defining an oil ventilating space;

a hydraulic clearance compensating device including a cylinder having a horizontally disposed longitudinal axis, and a piston mounted within said cylinder for axial displacement therein, said piston having means formed therein defining an antechamber;

means forming a fluid-tight connection between said antechamber and said oil ventilating space in said rocker arm;

said cylinder and said piston each having an internal end defining therebetween a pressure chamber;

a fluid passage formed in said internal end of said piston for communicating between said antechamber and said pressure chamber;

a check valve acting on said fluid passage for permitting fluid flow from said antechamber to said pressure chamber but blocking fluid flow from said pressure chamber to said antechamber;

said piston and said cylinder each having a cylindrical wall defining therebetween a ring gap;

a recess formed in said cylindrical wall of said piston;

and

an opening formed in said piston communicating between said antechamber and said recess for recycling oil leaking from said pressure chamber through said ring gap back into said antechamber.

5. A hydraulic clearance compensating system as defined in claim 4, wherein:

said oil ventilating space has a volume at least equal to the volume of said pressure chamber. 

1. A hydraulic clearance compensating system for controlling the motor valves of an internal combustion engine, comprising: a rocker arm having an oil flow channel and an oil ventilating space formed therein; a hydraulic clearance compensating device iNcluding a cylinder and a piston which is longitudinally displaceable with said cylinder, said piston and cylinder having a ring gap therebetween; an antechamber in said piston; means, including a port in said antechamber, sealingly communicating with said rocker arm for establishing a fluidtight oil flow path between said antechamber and said oil ventilating space; a pressure chamber adjacent one end of the cylinder which is communicatively connected to said antechamber within the piston by means of a non-return valve, said antechamber having means to hold oil supplied by said rocker arm, said antechamber receiving oil solely by way of said oil flow path and a transverse bore means communicating between the ring gap and the antechamber by which oil leaking from the pressure chamber is recycled back to the antechamber, the antechamber being otherwise sealed and having means to exclude air from said antechamber and said pressure chamber.
 2. A device as claimed in claim 1 wherein the ventilating space has a volume which is at least equal to the volume of oil capable of being held in the pressure chamber.
 3. A hydraulic clearance compensating system for controlling motor valves of an internal combustion engine having a pressurized oil supply system, comprising: a rocker arm including means therein defining an oil ventilating space, said ventilating space being fed with oil from the oil supply system and having means such that, when the oil supply system is depressurized, the oil in said ventilating space does not drain out through the oil supply system; a hydraulic clearance compensating device including a cylinder and a piston longitudinally displaceable within said cylinder, said piston and cylinder having a ring gap therebetween; means in said piston defining an antechamber; a pressure chamber in said cylinder adjacent one end thereof; fluid passage means communicating between said antechamber and said pressure chamber; a non-return valve in said fluid passage for permitting oil flow through said passage only toward said pressure chamber; said antechamber communicating with said ventilating space and having means to receive and hold oil supplied through said ventilating space in said rocker arm; means to recycle oil leaking from said pressure chamber through said ring gap back into said antechamber; said recycling means including a recess formed on the exterior of said piston in said ring gap; means defining at least one transverse bore communicating between said recess and said antechamber; a seal disposed in said ring gap and located adjacent the side of the recess remote from the non-return valve.
 4. A hydraulic clearance compensating system for controlling the motor valves of an internal combustion engine, comprising: a rocker arm pivotally mounted on a shaft having a horizontal axis, said rocker arm having means formed therein defining an oil ventilating space; a hydraulic clearance compensating device including a cylinder having a horizontally disposed longitudinal axis, and a piston mounted within said cylinder for axial displacement therein, said piston having means formed therein defining an antechamber; means forming a fluid-tight connection between said antechamber and said oil ventilating space in said rocker arm; said cylinder and said piston each having an internal end defining therebetween a pressure chamber; a fluid passage formed in said internal end of said piston for communicating between said antechamber and said pressure chamber; a check valve acting on said fluid passage for permitting fluid flow from said antechamber to said pressure chamber but blocking fluid flow from said pressure chamber to said antechamber; said piston and said cylinder each having a cylindrical wall defining therebetween a ring gap; a recess formed in said cylindrical wall of said piston; and an opening formed in said piston communicating between said antechamber and said recess For recycling oil leaking from said pressure chamber through said ring gap back into said antechamber.
 5. A hydraulic clearance compensating system as defined in claim 4, wherein: said oil ventilating space has a volume at least equal to the volume of said pressure chamber. 